gi6 'Appendix II.
Rider Engine, Fig. 879, which has been much used for small
powers, c is a displacer, and D the power plunger, their cranks
being about 90° apart. At F is a fire (hot body), at E a water
jacket (refrigerator), and H is the regenerator; the cycle being
essentially that of Stirling, and the operations as follows :—
1. Air compressed in D takes heat and expands: thus work
is done by the gas.
2. The air is transferred to c nearly at constant volume,
giving heat to H.
3. Air under c is compressed, losing heat to E : thus work is-
done on the gas.
4. The air is re-transferred to D at nearly constant volume,.
taking heat from H.